using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;

namespace STcpHelper.Packet
{
    public class STcpFileResPacket : ISTcpAsyncPacket
    {
        private string _path;

        public string FileName { get; private set; }
        public byte[] FileBinary { get; private set; }

        public STcpFileResPacket(string path)
        {
            this.FileName = Path.GetFileName(path);
            _path = path;
        }

        public STcpFileResPacket(byte[] dataBuffer, string path)
        {
            int cursor = 0;
            int nameLength = SBufferHelper.ConvertBufferToDataLength(dataBuffer, cursor);
            cursor += sizeof(int);

            this.FileName = SEncoding.GetString(dataBuffer, cursor, nameLength);
            cursor += nameLength;

            int fileSize = SBufferHelper.ConvertBufferToDataLength(dataBuffer, cursor);
            cursor += sizeof(int);

            this.FileBinary = new byte[fileSize];
            Array.Copy(dataBuffer, cursor, this.FileBinary, 0, fileSize);

            File.WriteAllBytes(path + @$"\{FileName}", this.FileBinary);
        }

        public async Task<byte[]> Serialize()
        {
            byte[] name = SEncoding.GetBytes(this.FileName);
            byte[] nameLength = SBufferHelper.ConvertDataLengthToBuffer(name.Length);
            byte[] data = await ReadFileAsync(_path);
            byte[] dataLength = SBufferHelper.ConvertDataLengthToBuffer(data.Length);

            int dataSize = STcpPacketHeader.GetDataSize(name, nameLength, data, dataLength);

            // 4bytes header
            STcpPacketHeader header = new STcpPacketHeader(PacketType.RES_FILE, dataSize);

            // [heaer][2byte name size][n bytes name][2bytes file size][n bytes string]
            return SBufferHelper.GetBuffer(STcpPacketHeader.HEADER_LENGTH + dataSize, header.Serialize(), nameLength, name, dataLength, data);
        }

        private async Task<byte[]> ReadFileAsync(string path)
        {
            using (FileStream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 1024, useAsync: true))
            {
                byte[] buffer = new byte[stream.Length];
                await stream.ReadAsync(buffer, 0, (int)stream.Length);
                return buffer;
            }
        }
    }
}